Cycle 13 Tough Problems Buzsaki Rhythms

May 01, 2012 12:04 PM  Excellent chapter... core reading.  read this regularly.

page 357  

Citicorp center...  had to damp the oscillations...  tuned mass damper.

Taipei 101 has a 730 ton tuned mass damper btwn floors 88 and 92.

Are oscillations just a BYPRODUCT.

thruout this volume  he tried to convince reader that they serve useful functions.

Evolution took advantage of the ease with which synchrony can be brot abt by oscillations

at mult tempral and spatial scales.

But... are oscil  CRITICAL for the emergence of the most complex brain opeations.

Brain without Oscilla;tions  page 358

page 359...

not poss to selectively eliminate oscilllations... cannot do this expt.

oscill are emergent... emerge in the whole brain but affect the parts.

but can synchrony be brought abt among neural assemblies without the rhythmic part.

marijuana... balanced reduction of  presyn release bo both GABA and glutamata...

elimiantes theta, gamma and ripple osc.

eg  computer, TV sets can run , in principles out oscil clocks but need some mech of coordiantion.

oscillations are ubiquitous in all brains... small and large...

oscil are a FREE source of synch and timing.

CONSCIOUSNESS

diff btwn a blink and a wink...

a WINK is a consc (voluntary) blink.

E Roy John def of  consc

page 361

multiple modalities of sensation and percetion are combined into a UNIFIED, Multimodal REPRES of the 

State of the System and Its Enviro and integrat3ed with memories and the needs of the organism,

generating emotional reacitons and program sof behavior to adjust the organism to its environment.

page 362 (his approach) 1st para:  brain systems that give rise to subjec consc experience

require special anatom connectivity and a special constell of oscillations that charac. the mammalian cerb cortex.

Networks that do NOT feel

HC:  relat RANDOM connectivyt of the HC = hiipocamp. is ideally suited for storing and recalling arbitrary events embedded

in a spatiotempr context

NEOCORTEX;  scalable, small-world architec of the neocortex can effect deal with statist regularities of enviro

to combine and bind features to make calcula decisions.

Essence of cortical opeation...  whatever compuation takes place locally... other part sof cortex get informed

due to intermed and long-range connex and oscil coupling mechs.

Conversely  self-oragnaized  (spontan) activity in large cortical aras  influences local processing of external inputs.

page 363  major claim of book that is that complex wiring of neocortex

supports it complex  (1/f)  self-organized network patterns.

cerebellum and basla ganglia do NOT have them.

CEREBELLUM:

same number of neurons as rest of brain combined!!!  (= 50B)

but occupies less than 10% of space in skull.

cerebellum is LOCALY ORGANIZEDS>

input from muscl spindles, tendons, noint, spnal paths, basal ganglia, etc.

RAPID EXECUTION of skilled mvmts at sppeds faster than can be controlled by "consc " sensory systems.

these comps are done in anter and post lobes  whereas  more ancient  flocculonodular lobe is concerned

with vestib function... posture and eye movements.

NO corp callos, no intermed or long-range paths.  no regional variations  (eg no brodmanns areas.

Cerebellum is NOT a mammalian invention..  all vertebrates have it and it serves an ident funciton.

excllent discussion o cerebellem... the best i've seen!!!  read later in detail!

BASALGANGLIA  365

cortex to basal ganglia to thalamocort paths...  major inhib loops.

p 367  best guess for comput role ... is that the neurons in the loops provide precise spike timing for the

numerically much smaller target neurons in these hubs.

the stircly local organiz of the loops provides high accurate temp coord for adjacent tragets only...

high preciison coordination of meighboring muscles.

page 368:

SUSTAINED ACTIVITY REQUIRES REGENERATIVE FEEDBACK

cerebel and basal gangla are INHIBITION-DOMINATED!!!  as opposed to

CORTICAL NETWORKS...  for  former cannot sustain  large-scale, self-organized

spontan patterns.

cerebellum...  very LOW amplitude mean LFPs!  cannost sustain  rhythms.

Never get epileptics dischanges from GABA dominated cerebellar or BG networks!

the antithesis of cortex... dominated by perpetual spont acitvity

and tempor coordination over wide spatial domains.

page 369:

ONLY STRUCTURES THAT DISPLAY  PERSISTENT NEURONAL ACTIVITY

and Involve Large Neuron Pools Support CONSC !!!

only special architectures like cerebral cortex can support  spatially widespread oscillats at

multiple temporal scales with the consequent  1/f  self-organized criticality features.

Global collective decisions require cooper actions of both neighboring and distant areas.

Flexible cooperation among local and distant cell assemblies  an essential ingredient for consc experience.

If not long-range connectivity exist AND/OR  if activity cannot persist for a sufficient amt of time, localy gen activty cannot engage distant neurons  therefore integration of info over a large neuro space cannot take place.

Regener activity requires + excit feedback,  a critical ingredient conspicuously absent in cerebellar and BG circuits.

Regen feedback can incorporate  the PAST into the systems present state so it threads both time and space...

allowing input induced perturbs to be compared to past similar encounters.

so this reconstruc feedback and sustained neuronal activ can place inputs into context.

Most strinking behavior of CORICAL NETWORKS is their regenrative sponat activity.

Every spike - snesory evoked or sponatn, in cortical princ. cells can reach distant neurons.

If spontaneous cortical activity is perturbed by a stimulus for a sufficiently long time

in large enuf neuronal space, it will be noticed;  ie  we become aware of it. ...

this spontaneous, self-organizing ability of cortical newrosk is what gives rise to orginality and freedom in the brain.

in contrast to the abstract and arcane prob of consc,the issues involved in the interaction btwn

self-organized and evoked activity can be investigated empirically and systemically by

comparing the lifetime and expansion of an input in neuronal space.

page 370  footnote 27:  "for my money, understanding the self-organzing ability of the brain is the

most interesting challenge in science.  Wihtout such know....cannot ever resolve the deepestmysteries of the brain.

Sponatn activy alone does not give rise to consc.

p 371... (i don't bleieve his statement here; abt brain in a vat)

brains interax with the body and the physico-social environ tha provide stability and meaning to a subset of all poss

sponat brain states.

An explicit prediciton of the above is that

large numbers of neurons with small-world connectivity can give rise to regenerative, spontan activity of the 1/f type and

this self-organized activ is a potnetial source of CONSC.

depends on size of network.

Lack of LR = long-range connex and intermit local bursts in premature babies => absence of consc.

Perinatal maturation of cortical anatomy and emergence of 1/f dyanmics offers the proper substrate

for gradual emerg. of self-awareness.   Also, poss in other mammals.